Biodegradable polymers have found use in a wide variety of applications ranging from trash bags that decompose in landfills to implantable medical devices that biodegrade in the body. Most of these applications require that such polymers have adequate physical properties and stability to provide for suitable handling and utility prior to being subjected to end use conditions that promote biodegradation. Further, it is often preferable that these same polymers rapidly or controllably biodegrade once subjected to such end use conditions. In addition, it is often desired that biodegradable polymers used for implantable medical devices be converted under physiological conditions to materials that do not irritate or harm the surrounding tissue. Many biodegradable polymers known in the art lack the combination of physical and/or chemical properties desired to meet the needs for specific applications.
For example, polylactide homopolymers (e.g., poly-L-lactide; PLA) and copolymers (e.g., poly(L-lactide-co-glycolide; PLGA) have been evaluated for use in making resorbable medical devices (e.g., vascular stents) because such polymers can offer sufficiently high tensile properties (e.g., modulus) at body temperature to allow for implantation of the medical device, and can biodegrade after implantation in the body. However, the use of such polylactides in implantable medical devices is practically limited by their brittleness.
There is a continuing need for new materials and methods having useful properties for making medical devices.